  html, body {
  margin: 0;
  padding:0;
  height: 100%
}

.sky {
  height: 480px;
  background: #007fd5;
  position: relative;
  overflow: hidden;
  -webkit-animation: sky_background 50s ease-out infinite;
  -moz-animation: sky_background 50s ease-out infinite;
  -o-animation: sky_background 50s ease-out infinite;
  animation: sky_background 50s ease-out infinite;
  -webkit-transform: translate3d(240,230,140);
  -ms-transform: translate3d(240,230,140);
  -o-transform: translate3d(240,230,140);
  transform: translate3d(240,230,140);
}

.sky .clouds_one {
  position: absolute;
  left: 0;
  top: 0;
  height: 100%;
  width: 300%;
  -webkit-animation: cloud_one 50s linear infinite;
  -moz-animation: cloud_one 50s linear infinite;
  -o-animation: cloud_one 50s linear infinite;
  animation: cloud_one 50s linear infinite;
  -webkit-transform: translate3d(240,230,140);
  -ms-transform: translate3d(240,230,140);
  -o-transform: translate3d(240,230,140);
  transform: translate3d(240,230,140);
}

.sky .clouds_two {
  position: absolute;
  left: 0;
  top: 0;
  height: 100%;
  width: 300%;
  -webkit-animation: cloud_two 75s linear infinite;
  -moz-animation: cloud_two 75s linear infinite;
  -o-animation: cloud_two 75s linear infinite;
  animation: cloud_two 75s linear infinite;
 -webkit-transform: translate3d(240,230,140);
  -ms-transform: translate3d(240,230,140);
  -o-transform: translate3d(240,230,140);
  transform: translate3d(240,230,140);
}

.sky .clouds_three {
  position: absolute;
  left: 0;
  top: 0;
  height: 100%;
  width: 300%;
  -webkit-animation: cloud_three 100s linear infinite;
  -moz-animation: cloud_three 100s linear infinite;
  -o-animation: cloud_three 100s linear infinite;
  animation: cloud_three 100s linear infinite;
  -webkit-transform: translate3d(240,230,140);
  -ms-transform: translate3d(240,230,140);
  -o-transform: translate3d(240,230,140);
  transform: translate3d(240,230,140);
}

@-webkit-keyframes sky_background {
  0% {
	background: #007fd5;
	color: #007fd5
  }
  50% {
	background: #16b636;/* 转换的颜色 */
	color: #a3d9ff
  }
  100% {
	background: #007fd5;
	color: #007fd5
  }
}
@-moz-keyframes sky_background {
  0% {
	background: #007fd5;
	color: #007fd5
  }
  50% {
	background: #16b636;/* 转换的颜色 */
	color: #a3d9ff
  }
  100% {
	background: #007fd5;
	color: #007fd5
  }
}
@keyframes sky_background {
  0% {
	background: #007fd5;
	color: #007fd5
  }
  50% {
	background: #16b636;/* 转换的颜色 */
	color: #a3d9ff
  }
  100% {
	background: #007fd5;
	color: #007fd5
  }
}

@-webkit-keyframes cloud_one {
  0% {
	left: 0
  }
  100% {
	left: -200%
  }
}
@-moz-keyframes cloud_one {
  0% {
	left: 0
  }
  100% {
	left: -200%
  }
}
@keyframes cloud_one {
  0% {
	left: 0
  }
  100% {
	left: -200%
  }
}

@-webkit-keyframes cloud_two {
  0% {
	left: 0
  }
  100% {
	left: -200%
  }
}
@-moz-keyframes cloud_two {
  0% {
	left: 0
  }
  100% {
	left: -200%
  }
}
@keyframes cloud_two {
  0% {
	left: 0
  }
  100% {
	left: -200%
  }
}

@-webkit-keyframes cloud_three {
  0% {
	left: 0
  }
  100% {
	left: -200%
  }
}
@-moz-keyframes cloud_three {
  0% {
	left: 0
  }
  100% {
	left: -200%
  }
}
@keyframes cloud_three {
  0% {
	left: 0
  }
  100% {
	left: -200%
  }
}